As a method for demolishing a tank, for example, Japanese Patent Laid-open No. 62-185965 describes a method comprising: shearing a side wall of a tank at a lower portion thereof to divide the tank into upper and lower sections along a spiral shear line provided on the periphery of the tank and a shear line connecting the starting and ending points thereof, interposing at a spiral shear region a rotation member that rotationally support the upper section of the storage tank, and successively cutting off the upper section of the storage tank in the form of an extension of the spiral on the upper side wall of the storage tank including a stepped portion of the shear line while rotating the upper section of the storage tank such that the stepped portion of the shear line approaches.
In addition, Japanese Patent Laid-open No. 5-280204 describes a method in which a side wall of a tank is separated from a bottom plate thereof, and the side wall is sheared spirally in the direction from the lower end to the upper end while being temporarily supported by, for example, a jack, to remove the cut-off piece.
According to the method described in the above-mentioned Japanese Patent Laid-open No. 62-185965, no link operation is necessary with a jack and thus there is no danger which otherwise may be involved in operation of the jack. However, it is not easy to interpose the rotary support member at the spiral cut-off region and to rotate the upper section of the tank.
On the contrary, according to a demolition method described in the above-mentioned Japanese Patent Laid-open No. 5-280204, operation can be made safely and easily because it is not necessary to interpose the rotary support member and to rotate the upper section of the storage tank. However, the demolition requires a significant time due to the necessity of the temporary support of the side wall by means of, for example, the jack.
In addition, demolition of a tank through, for example, fusing by an operation is time-consuming. Furthermore, meticulous care and much effort are required to ensure safety for the operator.
Taking these into consideration, the demolition of tanks is made by using a mechanical force rather than manpower. Such a technique has thus been desired that ensure safe and easy demolition of tanks effectively in a short period of time, while significantly enhancing safety and saving much labor.